What's the difference between an ADU and a JADU?

An ADU (Accessory Dwelling Unit) is a fully independent second home up to 1,200 sq ft on your lot, with its own kitchen, bath and entrance. A JADU (Junior ADU) is carved out of the existing house, capped at 500 sq ft, and may share a bathroom with the main residence. Most LA lots can build one of each.

Do I need to know LADBS, LADWP and BSS to permit an ADU?

You'll see all three. LADBS issues the building permit, LADWP handles water and power connections, and BSS clears the sewer lateral. Your designer or contractor coordinates each agency — but knowing the acronyms helps you read the plan-check correction letter.

Is Title 24 the same as the energy code?

Title 24 Part 6 is California's energy code. Every new ADU has to demonstrate compliance, which usually means high-performance windows, heat-pump HVAC, heat-pump water heating, and a small solar array. Compliance is documented by a Title 24 consultant and stamped on the plans.

What does HCD have to do with my backyard ADU?

HCD (California Department of Housing and Community Development) writes the statewide ADU rules that override most local zoning. When the city says 'no,' HCD's standards usually say 'yes' — which is why ministerial approval exists in the first place.

Why does the glossary include financing terms like HELOC and DSCR?

Permitting is only half the project. Most ADU homeowners finance through a HELOC, a cash-out refi, or a DSCR investor loan that underwrites against the unit's projected rent. Knowing the lender vocabulary saves weeks during underwriting.

What does Title 24 actually require for a new ADU?

Title 24 Part 6 forces every new ADU to model below a Title 24 baseline energy budget, which in 2025 effectively means heat-pump space heating, heat-pump water heating, high-performance windows (U≤0.30, SHGC≤0.23), and on-site solar unless the lot or roof orientation qualifies for an exception. A CalCERTS-registered HERS rater verifies install before final inspection.

Will an ADU trigger a full property tax reassessment?

No. Under California Revenue & Taxation Code §75 and BOE Rule 463, only the new construction value of the ADU is added to the assessment roll — your primary residence keeps its Prop 13 base year. Expect roughly 1–1.25% of the ADU's assessed cost as new annual property tax in LA County.

When does an SB9 lot split beat building an ADU?

SB9 splits work when you want two separate fee-simple parcels you can sell independently. ADUs win when you want rental income without losing yard or splitting title. SB9 also requires the homeowner to occupy one of the resulting units for at least three years; ADUs no longer carry an owner-occupancy requirement under AB 976.

Vol. I · Reference

The ADU glossary.

50 terms every Los Angeles homeowner runs into during permitting, design, construction and financing — defined in plain English.

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50 of 50 terms

A

AB 68 / AB 881 / AB 670Legal & Compliance: California statutes that streamlined ADU permitting starting 2020 — capped review timelines, prohibited HOA bans, and required ministerial approval for compliant units.
ADUAccessory Dwelling UnitPermits & Zoning: A self-contained second home on a lot zoned for one or more primary residences. Includes its own kitchen, bathroom, sleeping area and entrance.
Appraisal GapFinancing: Shortfall between an ADU's contracted construction cost and the post-build appraised value. Increasingly rare in LA — recent comps usually appraise ADUs at or above cost.
Attached ADUDesign & Construction: An ADU sharing one or more walls with the primary residence. Often cheaper to build than detached because utility runs are shorter.

B

BSSBureau of SanitationPermits & Zoning: LA agency that clears sewer-lateral capacity and stormwater discharge for new construction. ADU plans route through BSS in parallel with LADBS plan check.
Building EnvelopeDesign & Construction: The physical separator between conditioned interior space and the outdoors — walls, roof, slab, windows and doors. Envelope performance drives Title 24 compliance.

C

Cash-Out RefiFinancing: Refinancing the primary mortgage for more than the current balance and taking the difference as cash. Resets your interest rate — best when current rates are favorable.
Certificate of OccupancyC of OPermits & Zoning: Document issued by LADBS confirming the ADU may be lawfully occupied. Required by most lenders before a refinance and by short-term rental platforms before listing.
CorrectionsPermits & Zoning: Items the plan checker requires the design team to revise. Most projects clear two to three rounds; a clean first submittal can shorten approval by weeks.

D

Detached ADUDesign & Construction: A standalone ADU separated from the primary residence. Most flexibility on layout and the highest market rent — typically the highest ROI configuration in LA County.
Draw ScheduleFinancing: Phased disbursement of construction loan funds tied to inspection milestones. Typical ADU project sees 5–7 draws across the build.

E

EasementLegal & Compliance: Recorded right allowing a third party (utility, neighbor, city) to use part of your lot. ADUs cannot be built over easements — title and survey work flag them before design.
EV-Ready CircuitUtilities & Site: Dedicated 240V circuit and conduit roughed in for future EV charger installation. CALGreen requires at least one EV-ready space for new ADUs with parking.

F

FARFloor Area RatioPermits & Zoning: Ratio of total building floor area to lot area. ADUs of 800 sq ft or smaller are exempt from FAR limits under state law.

G

Garage ConversionDesign & Construction: Converting an existing attached or detached garage into an ADU. Existing footprint is preserved; setback and parking requirements are typically waived under state law.
Geotech ReportDesign & Construction: Soil and slope study required on hillside lots and many flatland projects. Drives foundation design and adds 2–4 weeks to early-stage work.

H

Heat PumpDesign & Construction: All-electric system that provides both heating and cooling. Title 24 effectively requires heat pumps in new ADUs in most LA climate zones.
HELOCHome Equity Line of CreditFinancing: Revolving credit line secured by your home equity. Common ADU financing path for homeowners with significant equity and a strong credit profile.

I

Impact FeesPermits & Zoning: Fees charged by the city to fund schools, parks and infrastructure. State law waives impact fees on ADUs under 750 sq ft.

J

JADUJunior Accessory Dwelling UnitPermits & Zoning: An ADU under 500 sq ft built within the existing walls of a primary home. May share a bathroom with the main house and requires owner-occupancy of either unit.

K

KitchenetteDesign & Construction: Compact efficiency kitchen — typically a 24-in cooktop, small sink and undercounter fridge. JADUs may use a kitchenette in lieu of a full kitchen; ADUs require a full one.

L

LADBSLos Angeles Department of Building and SafetyPermits & Zoning: City agency that reviews plans, issues permits and inspects construction inside the City of Los Angeles. ADU plans are routed through LADBS' standard plan check.
LADWPLA Department of Water and PowerUtilities & Site: Municipal utility serving the City of LA. Service upgrades for ADUs (panel changes, new meters) often require LADWP coordination separate from the building permit.
Lien ReleaseLegal & Compliance: Document signed by a contractor or supplier waiving their right to file a mechanic's lien against the property. Required at each draw to protect the homeowner.

M

Ministerial ApprovalLegal & Compliance: A permit granted on objective standards alone — no public hearing, no neighbor notice, no discretionary review. State law mandates ministerial approval for compliant ADUs.

N

NHD ReportNatural Hazard DisclosureLegal & Compliance: California-mandated disclosure of flood, fire, seismic and landslide zones affecting a property. Required at any sale and frequently re-pulled for ADU lender underwriting.

O

Owner-OccupancyLegal & Compliance: Requirement that the property owner live in either the primary home or the ADU. Currently waived for ADUs permitted between 2020–2024 in California; required for all JADUs.

P

Panel UpgradeUtilities & Site: Replacing the home's main electrical panel to handle additional load. ADUs with full kitchens and EV charging frequently push older 100A panels past capacity.
Performance BondLegal & Compliance: Surety guaranteeing the contractor will complete the project per contract. Rarely required on residential ADUs but offered as an upgrade by select builders.
Plan CheckPermits & Zoning: The structured review of architectural, structural, electrical, plumbing and mechanical plans by LADBS. State law caps residential ADU review at 60 days.
Punch ListDesign & Construction: Final list of incomplete or imperfect items the contractor must resolve before final payment. A well-run project has fewer than 30 punch items at substantial completion.

Q

Qualified MortgageQMFinancing: CFPB loan category that meets ability-to-repay rules — capped points/fees, no toxic features. Most ADU refis and HELOCs are originated as QM loans for safer pricing.

R

Renovation LoanFinancing: Construction-to-permanent loan that funds the build and converts to a standard mortgage on completion. Common products: Fannie Mae HomeStyle, Freddie Mac CHOICERenovation.

S

SB 9Legal & Compliance: California statute (effective 2022) allowing lot splits and up to two units on most single-family parcels. Layered with ADU law, a lot can sometimes accommodate four homes.
School FeesPermits & Zoning: Per-square-foot fee assessed by the local school district on new habitable area. Waived on ADUs under 500 sq ft and discounted on units 500–750 sq ft.
Service DropUtilities & Site: The overhead or underground line bringing utility power from the street to the property. Larger ADUs may require an upgraded service drop scheduled by the utility.
SetbackPermits & Zoning: Minimum distance a structure must sit from a lot line. State law caps ADU side and rear setbacks at 4 ft regardless of local zoning.
Sewer LateralUtilities & Site: The underground pipe connecting a property to the city sewer main. ADUs typically tie into the existing lateral; capacity is verified during plan check.
Soft-Story RetrofitDesign & Construction: Seismic strengthening of a building with a weak ground floor — typical for properties with tuck-under parking. Often triggered when adding an attached ADU above.
Solar PVDesign & Construction: Photovoltaic panels generating electricity. Required on most new construction in California; ADUs attached to a primary home with existing solar can sometimes share the array.

T

Title 24Design & Construction: California's Building Energy Efficiency Standards. Governs insulation, glazing, HVAC efficiency, and solar requirements — recalibrated every three years.
Title PolicyFinancing: Insurance protecting the homeowner and lender against undiscovered claims on the property. Required at closing for any ADU-related refinance or HELOC.

U

UnderwritingFinancing: Lender's review of credit, income, appraised value and DTI before approving an ADU loan. Construction-loan underwriting also evaluates plans, budget and contractor.
Utility Connection FeeUtilities & Site: One-time charge by LADWP, SoCalGas or BSS to extend or upsize service to a new ADU. Typical range in LA is $2,500–$15,000 depending on meter and lateral work required.

V

VariancePermits & Zoning: Discretionary approval to deviate from a zoning standard. Compliant ADUs almost never need one — state law guarantees ministerial approval against objective rules.

W

Water Meter UpgradeUtilities & Site: Replacing the existing LADWP water meter with a larger one to serve both the primary home and the ADU. Triggered by combined fixture-unit counts above the meter's rating.

X

XeriscapeDesign & Construction: Low-water landscape design using drought-tolerant planting and permeable surfaces. LADWP turf-replacement rebates often offset xeriscape work folded into the ADU site plan.

Y

Yard SetbackPermits & Zoning: Planner shorthand for the required clear distance between a structure and the front, side or rear lot line. State ADU law caps side and rear yard setbacks at 4 ft.

Z

Zero Lot LineDesign & Construction: Configuration where a structure sits directly on a property line with no setback. Rare for ADUs — typically requires a fire-rated wall and recorded neighbor agreement.
ZoningPermits & Zoning: Municipal designation (e.g. R1, RD1.5, R2) defining what may be built on a lot. State ADU law overrides most local zoning for one ADU plus one JADU on single-family lots.

FAQ

Frequently asked questions

The acronyms behind the acronyms — quick answers to the questions homeowners ask most.

What's the difference between an ADU and a JADU?
An ADU (Accessory Dwelling Unit) is a fully independent second home up to 1,200 sq ft on your lot, with its own kitchen, bath and entrance. A JADU (Junior ADU) is carved out of the existing house, capped at 500 sq ft, and may share a bathroom with the main residence. Most LA lots can build one of each.
Service types →Run the ROI math →
Do I need to know LADBS, LADWP and BSS to permit an ADU?
You'll see all three. LADBS issues the building permit, LADWP handles water and power connections, and BSS clears the sewer lateral. Your designer or contractor coordinates each agency — but knowing the acronyms helps you read the plan-check correction letter.
Permit & design step →Cost breakdown →
Is Title 24 the same as the energy code?
Title 24 Part 6 is California's energy code. Every new ADU has to demonstrate compliance, which usually means high-performance windows, heat-pump HVAC, heat-pump water heating, and a small solar array. Compliance is documented by a Title 24 consultant and stamped on the plans.
Where the budget goes →
What does HCD have to do with my backyard ADU?
HCD (California Department of Housing and Community Development) writes the statewide ADU rules that override most local zoning. When the city says 'no,' HCD's standards usually say 'yes' — which is why ministerial approval exists in the first place.
All FAQs →
Why does the glossary include financing terms like HELOC and DSCR?
Permitting is only half the project. Most ADU homeowners finance through a HELOC, a cash-out refi, or a DSCR investor loan that underwrites against the unit's projected rent. Knowing the lender vocabulary saves weeks during underwriting.
Compare loan products →ROI calculator →
What does Title 24 actually require for a new ADU?
Title 24 Part 6 forces every new ADU to model below a Title 24 baseline energy budget, which in 2025 effectively means heat-pump space heating, heat-pump water heating, high-performance windows (U≤0.30, SHGC≤0.23), and on-site solar unless the lot or roof orientation qualifies for an exception. A CalCERTS-registered HERS rater verifies install before final inspection.
Title 24 walkthrough →Where the budget goes →
Will an ADU trigger a full property tax reassessment?
No. Under California Revenue & Taxation Code §75 and BOE Rule 463, only the new construction value of the ADU is added to the assessment roll — your primary residence keeps its Prop 13 base year. Expect roughly 1–1.25% of the ADU's assessed cost as new annual property tax in LA County.
Reassessment math →ROI calculator →
When does an SB9 lot split beat building an ADU?
SB9 splits work when you want two separate fee-simple parcels you can sell independently. ADUs win when you want rental income without losing yard or splitting title. SB9 also requires the homeowner to occupy one of the resulting units for at least three years; ADUs no longer carry an owner-occupancy requirement under AB 976.
ADU vs SB9 comparison →